The State's Part Locator might be able to help you find a Intake Manifold Runner Control for your Ford Mustang Cobra in order to bring it into compliance with state law.
If they are unable to find you a new or used IMRC and find that that is the only reason your Mustang is failing the smog test, they may be able to issue you a "Limited Parts Exemption". In most cases the needed parts are found. You may contact the State Smog Check Parts locator by calling 800–622–7733.